well you could just use fopen to read the file into a string, then echo it
you could also use
echo file_get_contents()
prob the simplest and maybe most efficient way would be to use readfile() which will output the contents of the file directly.
you will need to send the proper mime header(s) before streaming out the file though
i dont know the proper headers offhand but im sure if you read the user comments for header() you will find them.